Attempts are being made to find a suitable animal model for human sickle cell disease. Blood from several species of deer is being tested for induction of erythrocyte sickling. Deer blood is also being studied rheologically in vitro. The animals will then have hemodynamic studies performed under general anesthesia before and during sickling. Cardiac output (by dye dilution), distribution of blood flow (by nuclide-labeled microspheres) and blood pressure in systemic and pulmonary arteries will be measured before and after the induction of sickling. These animals will be sacrificed and postmortem examinations carried out. The effects of vasodilator drugs, sympathetic blocking agents and other maneuvers will then be evaluated.